Concentrating Solar Power: Current Cost and Future Directions

Transcription

1 Concentrating Solar Power: Current Cost and Future Directions Craig Turchi CSP Systems Analysis Task Leader Thermal Systems R&D Group May 30, 2017

2 Topics NREL s System Advisor Model (SAM) CSP costs CSP research directions o Molten salts and other heat storage media o Advanced power cycles o Plant configuration and value optimization NATIONAL RENEWABLE ENERGY LABORATORY 2

3 SAM The System Advisor Model (SAM) is a performance and financial model designed to facilitate decision making for people involved in the renewable energy industry. NATIONAL RENEWABLE ENERGY LABORATORY 3

4 NREL 2016 CSP Cost Survey Questioned CSP developers and stakeholders regarding the current cost of CSP Values used to keep SAM s cost inputs up-to-date Separate sections for power tower, parabolic trough, and linear Fresnel systems Survey Number of Total Questions with 3 respondents questions responses Power Tower 20* (100%) Parabolic Trough 20* (58%) Linear Fresnel * The 20 respondents were not all the same for each technology NATIONAL RENEWABLE ENERGY LABORATORY 4

5 SAM Changes: Power Towers Power Tower (Molten Salt and DSG) SAM 2016 SAM 2017 Responses Comments/Justification Site Improvements $/m2 16 no change 11 Heliostat Field $/m Wide variability in responses Tower cost formula no change 11 Receiver cost formula 10 Reduce DSG by about 10%, MS by lesser amount Receiver reference cost (MS) $ 110,000, ,000,000 Receiver cost scaling exponent 0.7 no change Receiver reference cost (DSG) $ 55,402,800 48,800,000 Receiver cost scaling exponent 0.7 no change Thermal energy storage $/kwh-t Power cycle $/kwe Balance of plant $/kwe 340 no change 11 Contingency % 7 no change 15 EPC & Owners Cost % Sales Tax % 5 no change 13 5% applied to 80% of direct costs O&M Fixed cost by capacity (MS) $/kw-yr 66 no change 7 O&M Fixed cost by capacity (DSG) $/kw-yr Variable cost O&M (both) $/MWh Property Tax % 0 no change 7 Insurance % 0.5 no change 7 Min. turbine operation % Max. turbine over design % 105 no change 12 reviewers recommend 0-1.2%, but left at 0% to match other SAM models NATIONAL RENEWABLE ENERGY LABORATORY 5

6 Number of people Heliostat Field Cost 7 Question: Current installed cost for heliostat field = 170/m 2? Way too High (>25%) A little too High (>10%) About Right ( ± 10%) A little too Low (<10%) Way too Low (<25%) No Opinion (includes Blank) New SAM value = $145/m 2 NATIONAL RENEWABLE ENERGY LABORATORY 6

7 CSP Costs: SAM 2016 vs. SAM 2017 SAM Model with default values Total Overnight Installed Cost ($/kw) SAM SAM % change Physical Trough (6 h thermal storage) 6,705 6, % Molten Salt Tower (10 h thermal storage) 7,365 6, % Direct-Steam Tower (no thermal storage) 4,710 4, % Costs assume construction in the southwest region of the United States Applying SunShot financial assumptions (see On the Path to SunShot, NREL/TP , 2016), the lowest levelized cost of energy corresponds to the molten salt power tower with a value of approximately 110 USD/kWh. NATIONAL RENEWABLE ENERGY LABORATORY 7

8 SunShot CSP Gen3 Technology Roadmap NATIONAL RENEWABLE ENERGY LABORATORY 8

9 Molten Salt Options for Higher Temperature Operation Salt Melting Point (C) Maximum Temp (C) Heat Capacity (J/g-K) Density (kg/l) Viscosity (cp) Relative ρ*c p (-) Solar Salt (NaNO 3 /KNO 3 ) 220 ~ KNO ~650? KCl/MgCl > KCl/NaCl/MgCl > ZnCl 2 /KCl/NaCl 199 > Na 2 CO 3 /K 2 CO 3 /Li 2 CO ~ Physical properties estimated/measured near 600 C for comparison Data sources: Solar salt: SQM solar thermal salts factsheet Mg chlorides: ORNL/TM-2006/69; Serrano-Lopez et al. (2013); Gowtham Mohan et al. (2017 submitted) Zn chlorides: University of Arizona (private correspondence) Carbonates: An et al. (2016) NATIONAL RENEWABLE ENERGY LABORATORY 9

10 New Molten Salt Benefits/Challenges Salt Primary Benefit vs Solar Salt Primary Challenges KNO 3 Slightly better thermal stability ( ºC) Slightly higher T mp Slightly higher cost KCl/MgCl 2 KCl/NaCl/MgCl 2 ZnCl 2 /KCl/NaCl Na 2 CO 3 /K 2 CO 3 /Li 2 CO 3 Lower salt cost Better thermal stability Lower salt cost Better thermal stability Slightly lower T mp Better thermal stability Higher ρ*c p (smaller tanks) Better thermal stability Higher T mp Lower ρ*c p (i.e., larger tanks) Corrosion Higher T mp Lower ρ*c p Corrosion Lower ρ*c p Corrosion Measureable vapor pressure Slightly higher salt cost Higher T mp Corrosion High salt cost (Li 2 CO 3 ) Laboratory testing indicates Cl corrosion can be controlled if high purity is maintained in the salt melt NATIONAL RENEWABLE ENERGY LABORATORY 10

11 Falling Particle Power Tower Systems Advantages No freezing concerns No trace heating Thermally stable particles Direct heating of particles allows for high flux/concentration ratios Direct storage of inexpensive particles Particle handling, heat exchange, and storage techniques well established Challenges Less established within CSP industry Particle durability, attrition (dust emission) Receiver efficiency via convective/radiative and particle losses Increase particle/wall heat transfer Particle-to-sCO 2 heat exchanger at 700ºC, 20 MPa NATIONAL RENEWABLE ENERGY LABORATORY 11

12 CSP Power Cycle Development The supercritical-co 2 Brayton cycle promises higher efficiency and lower installed cost versus to existing superheated steam cycle $100 million cost-shared project is to build and demonstrate a 10 MW e system in Texas Cycle performance gains are more pronounced at higher temperatures; U.S. DOE program is targeting 700ºC turbine inlet temperature NATIONAL RENEWABLE ENERGY LABORATORY 12

13 Price signal Power to Grid System Operation/Dispatch Optimization Simple Optimized Metric Simple Optimized Annual energy (year 1) 301,600 MWh 289,300 MWh Levelized Cost of Energy (real) 11.9 /kwh 12.4 /kwh Power Purchase Agreement price (year 1) 9.6 /kwh 5.9 /kwh Despite lesser generation, optimized dispatch produces greater value as indicated by a lower acceptable PPA price Matching CSP system design and dispatch to grid demand is essential NATIONAL RENEWABLE ENERGY LABORATORY 13

14 Thank you! NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

15 sco 2 Cycle Development under STEP DOE s STEP project will demonstrate a 10 MW e sco 2 recompression cycle Supercritical Transformational Electric Power Image: Southwest Research Institute NATIONAL RENEWABLE ENERGY LABORATORY 15

16 STEP Test Facility Attributes and Objectives 10 MW e sco 2 recompression Brayton cycle Turbine inlet temperature of 700 C Demonstrate pathway towards an overall power cycle efficiency of 50% or greater Reconfigurable and can monitor and characterize primary components or subsystems (turbomachinery, heat exchangers, recuperators, bearings, seals, etc.) Demonstrate steady state, transient load following, and limited endurance operation. Capable of test campaigns to assess critical component degradation mechanisms to assess component life and cost NATIONAL RENEWABLE ENERGY LABORATORY 16

17 sco 2 Recompression Cycle Design-point values from DOE-funded CSP Gen3 analysis report by Black & Veatch T amb = 22.5 C 715 C 249 bar 35 C 81 bar > 720 C 24 MW 574 C 85 bar 217 C 249 bar 86 C 256 bar 95 C 82 bar ~540 C 518 C 253 bar 267 C 84 bar 33 MW 19 MW Note: SunShot CSP plants are assumed to be dry cooled, so a higher design-point ambient temperature is likely. NATIONAL RENEWABLE ENERGY LABORATORY 17